1. Field of the Invention
The present invention relates to an ink supply device for use with a label printing and applying machine, usually of the portable type (hereinafter referred to as a "hand labeler").
2. Description of the Prior Art
In a hand labeler or a tag printing and applying machine, the printing types have been conventionally inked using a plurality of ink rollers which are impregnated with ink of the same or different colors. For example, U.S. Pat. No. Re. 27,889, of the inventor hereof, entitled "Portable One-Hand-Operable Labeling Machine" describes a dichromic inking process. Two printing heads are fixed to yokes which are swung up and down together by the actuation of a hand lever. There are two separated rotating arms, which respectively hold the two ink rollers. Each roller is impregnated with a different color ink. The rollers are independent and rotatable, with one roller in front of the printing heads and the other behind the printing heads. The separate roller supporting arms are pivotally mounted in the machine frame of the hand labeler. Each arm is urged by a respective spring against the respective type surface of the printing head.
Squeezing of the hand lever lowers the yokes, and with them the front and rear printing heads. This pushes aside the front and rear ink rollers and their respective spring biased rotating arms. The front ink roller inks the type surface of the front printing head, whereas the rear ink roller inks the type surface of the rear printing head. When the hand lever is further squeezed, it lowers the yokes until the type surfaces of the respective printing heads contact and print a label.
The rotating arm that supports the rear ink roller is placed so as to pivot substantially at the center of the inside of the machine frame of the hand labeler. This enlarges the size of the hand labeler. Further, attachment and removal of the rear roller supporting arm becomes so difficult as to defeat the usefulness of the labeler when it comes to replacement of the rear ink roller.
In U.S. Pat. No. 3,902,952, entitled "Hand Operated Labeler", there is a holder, in which two ink rollers impregnated with different color inks are rotatably mounted. The rollers are attached to a front portion of the hand labeler by a holder. The ink rollers are urged against the type surfaces by the action of a spring. The attachment and removal of the ink roller holder is facilitated.
However, both of the above systems have disadvantages. Since the ink rollers are brought into contact with the type surfaces only by the biasing force of the spring, the pressure of the ink rollers against the type surfaces becomes weaker as the biasing force of the spring weakens due to aging. The quality of the ink imprints deteriorates. Further, as the ink rollers are progressively less deeply depressed by the type surfaces, the ink is not pumped to the surfaces of the ink rollers. Only a small part of the available stored ink is usable. As a result, the ink rollers can be used for a limited number of labels only, thus rendering the reviewed hand labelers uneconomical.
If the hand lever is squeezed too swiftly, the ink rollers may be kept away from any contact with the type surfaces or may only have very weak contact. As a result, no imprint is obtained on the label or color shading differences occur across an imprint.
In U.S. Application Ser. No. 772,469, filed Feb. 28, 1977, of the inventor hereof, entitled "Ink Supply Mechanism for Dichromic Portable Labeling Machine", now U.S. Pat. No. 4,095,524 two different color ink rollers are provided and they use an effective forced ink-oozing system. However, attachment of new ink rollers and removal of exhausted ink rollers remains quite difficult. In this system, there is a pair of ink roller holding members, which are independently swingable and which are equipped with guide rollers. The holding members are fitted in retaining grooves at both sides of a front ink roller frame, which is attached to an ink roller assembly.
With the arrangement of this application, it is difficult to replace the ink rollers. In part, this is because the two holding members cannot be made integral. Even if a bridge member connecting the holding members into an integral structure is provided, the bridge member would collide with the front ink roller. Moreover, because the guide rollers are attached to the rear ink roller frame, it is difficult to preset only the guide rollers in the rear guide grooves, to then attach the ink roller assembly to the holding members and to subsequently attach the rear ink roller frame to that assembly.
Since the front and rear frame holders constituting the ink roller assembly are pivotally pinned so as to rotate relative to each other, it becomes more difficult to attach them to the rotatable holding members.
Other inking devices are disclosed in U.S. Application Ser. No. 716,934, filed Aug. 23, 1976, now abandoned and replaced by Ser. No. 3,626, filed Jan. 15, 1979, now U.S. Pat. No. 4,240,348 and particularly devices which are easier to remove and attach. But, these devices also have some of the problems discussed above.